KR20100022410A - Method and apparatus of tracking satellite signal - Google Patents

Abstract

The present invention relates to a satellite tracking device and method, comprising a plurality of tracking modules for generating correlation values by performing an integration operation in different integration time units based on satellite signals received from a satellite, based on correlation values. A plurality of tracking loops for generating distance measurements between the satellite and the satellite tracking device and signal to noise ratios (SNRs) for the satellite signal, and weights based on the SNRs, It includes a position calculation unit for calculating the position of the satellite tracking device by applying to.

Description

Method and device for satellite tracking {Method and Apparatus of tracking satellite signal}

The present invention relates to a satellite tracking device and method, and more particularly, to a satellite tracking device and method capable of responding to a change in the level of a satellite signal, and a computer-readable recording medium recording a program for executing the satellite tracking method. It is about.

The Global Navigation Satellite System (GNSS) is a system that accurately tracks the position of a target on the ground using a network of satellites flying in space. It is a conventional GPS system operated by the US Department of Defense. , The Galileo Positioning System under development around the European Union, and the Global Navigation Satellite System (GLONASS) operated in Russia. The satellite navigation system is widely used in the field of information and communication such as aircraft, ship positioning and telematics.

Typically, GPS is a satellite navigation system that provides location information using satellites orbiting space. GPS satellites are code division multiple access (CDMA) schemes in which four satellites are allocated to six orbits. The same frequency band is used to share the bands using different codes.

GPS receivers receive signals from at least three GPS satellites to determine the user's location. In general, a GPS receiver uses 12 to 16 tracking modules and assigns one tracking module to one satellite. One measurement is obtained. However, the tracking module has a fixed performance, and there is a limit even when the performance is variable.

SUMMARY OF THE INVENTION An object of the present invention is to provide a satellite tracking device and method for improving signal tracking performance according to a change in satellite signal level, and a computer-readable recording medium recording a program for executing the method. .

According to an aspect of the present invention, a satellite tracking device includes a plurality of tracking modules configured to generate correlation values by performing integration operations on different integration time units based on satellite signals received from satellites; A plurality of tracking loops for generating distance measurements between the satellite and the satellite tracking device and SNRs for the satellite signal based on the correlation values; And a position calculator configured to set weights based on the SNRs, and apply the weights to the distance measurement values to calculate a position of the satellite tracking device.

In addition, the satellite tracking method of the satellite tracking device according to the present invention for solving the above problems is performed by generating an integral operation by performing an integral operation for each integral time unit based on the satellite signal received from the satellite; Generating, using a plurality of tracking loops, distance measurements between the satellite and the satellite tracking device and SNRs for the satellite signal based on the correlation values; And calculating weights based on the SNRs and applying the set weights to the distance measurement values to calculate the position of the satellite tracking device.

In addition, the object of the present invention comprises the steps of: generating correlation values by performing integration operations on different integration time units based on satellite signals received from satellites; Using a plurality of tracking loops to generate distance measurements between the satellite and the satellite tracking device and SNRs for the satellite signal based on the correlation values; And calculating weights based on the SNRs and applying the set weights to the distance measurement values to calculate the position of the satellite tracking device. Is achieved by an existing recording medium.

According to the present invention, the satellite tracking device includes a plurality of sub-tracking modules assigned to a satellite signal received from one satellite, thereby obtaining a plurality of distance measurement values, and for the obtained plurality of distance measurement values. By applying weights, the optimal position can be calculated. As a result, the accuracy of the position of the satellite tracking device can be improved despite the change in the sensitivity of the satellite signal.

In addition, even if one secondary tracking module loses the satellite signal, the secondary tracking module using the other secondary tracking module allows the secondary tracking module that lost the satellite signal to quickly reacquire and track the satellite signal, thereby improving the accuracy of the position of the satellite tracking device. Can improve.

With respect to the embodiments of the present invention disclosed in the text, specific structural to functional descriptions are merely illustrated for the purpose of describing embodiments of the present invention, embodiments of the present invention may be implemented in various forms and It should not be construed as limited to the embodiments described in.

Hereinafter, with reference to the accompanying drawings, it will be described in detail an embodiment of the present invention. The same reference numerals are used for the same elements in the drawings, and duplicate descriptions of the same elements are omitted.

Before describing embodiments of the present invention, the satellite tracking device and the satellite tracking method according to the present invention should be understood as a satellite tracking device and a satellite tracking method in a positioning system that determines a location using a signal received from an artificial satellite. Make it clear. That is, it should be understood as a satellite tracking device for determining a location by tracking satellite signals in the above-described GPS, Galileo positioning system, GLONASS, and the like. Hereinafter, a GPS receiver will be described as a location tracking device. However, the present invention is not limited thereto, and it is obvious that the present invention is applied to the Galileo positioning system and the satellite tracking device of GLONASS.

1 is a block diagram schematically illustrating a GPS receiver according to an embodiment of the present invention.

Referring to FIG. 1, the GPS receiver 1 according to an exemplary embodiment of the present invention may include an antenna 10, a radio frequency (RF) processor 20, a tracking module 30, and a tracking loop 40. And a position calculator 50.

The antenna 10 receives a signal transmitted from a GPS satellite. The RF processor 20 converts the signal received from the antenna 10 to an intermediate frequency (IF) in the RF domain. The tracking module 30 includes a plurality of main tracking modules each assigned to different satellites, and generates a correlation value from a signal output from the RF processor 20. The tracking module 30 may also be referred to as a correlator. do. The tracking loop 40 receives the correlation values generated by the tracking module 30, controls the tracking module 30, and generates distance measurements and signal to noise ratios (SNRs). The position calculator 50 receives the distance measurement value and the SNR generated by the tracking loop 40 to calculate an optimal position.

FIG. 2 is a block diagram illustrating a part of the GPS receiver of FIG. 1 in detail.

Referring to FIG. 2, the GPS receiver includes a tracking module 30, a tracking loop 40, and a position calculator 50.

The tracking module 30 includes a plurality of main tracking modules assigned to different satellites, that is, the first main tracking module 31 to the Nth main tracking module 32, and the first main tracking module 31. Each of the to N-th main tracking module 32 includes a plurality of auxiliary tracking modules. In one embodiment of the invention, each of the first main tracking module 31 to the Nth main tracking module 32 includes three sub tracking modules. However, this is only one embodiment of the present invention, and in other embodiments, each of the first main tracking module 31 to the Nth main tracking module 32 may include two or three or more sub tracking modules. .

In detail, the first main tracking module 31 includes a first sub tracking module 311, a second sub tracking module 312, and a third sub tracking module 313. Each of the first to third sub-tracking modules 311, 312, and 313 duplicates a pseudo noise code and a carrier wave, mixes it with a signal received from a satellite, and integrates the result into different integration times. For example, the integration time of the first sub-tracking module 311 is 1 ms, which is a period of Coarse / Acquisition (C / A) code, and the integration time of the second sub-tracking module 312 is 20 ms, which is a period of the data bit, The integration time of the third tracking module 313 may be set to 20 ms or more.

In other words, the first to third sub-tracking modules 311, 312, and 313 receive the signal converted to the intermediate frequency from the RF processor 20 and start the integration with an integration time of 1 ms. The first sub tracking module 311 continues the integration in the unit of integration time of 1 ms, and the second and third sub tracking modules 312 and 313 perform integration with an integration time of 20 ms. Then, once all subframes are acquired from the satellite, the third sub-tracking module 313 performs the integration with an integration time of 20 ms or more. Here, the bit synchronization is to find the transition position of the data bit based on the result value integrated in the unit of time of 1ms to start the operation at the position. Thus, the first sub tracking module 311 can track satellite signals up to -145 dBm, the second sub tracking module 312 can track satellite signals up to -153 dBm, and the third sub tracking module 313 Can track satellite signals up to -160dBm.

The tracking loop 40 includes a plurality of main tracking loops corresponding to the plurality of main tracking modules included in the tracking module 30, that is, the first main tracking loops 41 to the Nth main tracking loop 42. The first main tracking loop 41 includes first to third sub tracking loops 411, 412, 413 corresponding to the first to third sub tracking modules 311, 312, 313. The N th main tracking loop 42 includes first to third sub tracking loops 421, 422, 423 corresponding to the first to third sub tracking modules 321, 322, 323. As described above, in one embodiment of the present invention, since each main tracking module includes three sub tracking modules, each main tracking loop also includes three sub tracking loops. However, this is only one embodiment of the present invention, and in another embodiment, each main tracking loop may include sub tracking modules corresponding to the number of sub tracking modules.

Each of the first to third sub-tracking loops 411, 412, and 413 uses carriers and pseudo noise using data output from the first to third sub-tracking modules 311, 312, and 313, that is, correlation values. The code is tracked to control the first to third tracking modules 311, 312, and 313. In addition, each of the first to third sub tracking loops 411, 412, and 413 is a GPS receiver using data output from the first to third sub tracking modules 311, 312, and 313, that is, a correlation value. The distance between (1) and the satellite is measured to generate a distance measurement and an SNR.

More specifically, the first to third sub-tracking loops 411 to eliminate the delay between the pseudo noise code and the duplicated pseudo noise code of the satellite signal and to ensure that the frequency and phase between the carrier and the duplicated carrier of the satellite signal are the same. , 412 and 413 each calculates a frequency of a carrier generator and a code generator of the first to third sub-tracking modules 311, 312, and 313 to generate a control value, and uses the control value to generate the control value. Control the frequency of the code generator. For example, the first to third sub tracking loops 411, 412, and 413 may be applied with a frequency locked loop (PLL) or a phase locked loop (PLL) for carrier tracking, and a delay locked (DLL) for code tracking. Loop) may be applied.

As described above, since the first to third sub tracking modules 311, 312 and 313 integrate and output a signal with different integration times, the first to third sub tracking modules 411, 412, and 413 are integrated. Even if one of the first to third sub tracking modules 311, 312, and 313 loses a signal, the sub tracking module continuously updates the signal of the lost sub tracking module using data output from the other sub tracking module. As a result, when the secondary tracking module that loses a signal later acquires a signal, a control value, that is, a frequency control value of a carrier generator and a code generator, may be transmitted to reduce a time required for reacquisition of a signal. In other words, when the first to third sub tracking loops 411, 412, and 413 acquire a signal from the sub tracking module which lost the signal, the first sub tracking loops 411, 412, and 413 do not track the re-acquired signal again from the beginning. The tracking time can be shortened by allowing the tracking to be immediately performed using the output data.

Each of the first to third sub-tracking loops 411, 412, and 413 may have an SNR of one of the signals received from the first to third sub-tracking modules 311, 312, and 313 below a predetermined threshold. The secondary tracking module determines that the signal is lost. Since the integration time of the first sub tracking module 311 among the first to third sub tracking modules 311, 312, and 313 is the shortest, the SNR is often small, so that the first sub tracking module 311 receives a signal. In many cases, since the integration time of the third part tracking module 313 is the longest, most of the SNR is large, so that the signal is rarely lost.

For example, when the GPS receiver is located in an area where the signal is not sensitive, the first main tracking loop 41 receives data output from the first sub tracking module 311 performing an integration for an integration time of 1 ms. Cannot track satellite tracking. However, since the second and third sub-tracking modules 312 and 313 perform the integration for a sufficient integration time, the second and third sub-tracking loops 412 and 413 are continuous even if the signal is not sensitive. Since the signal can be tracked by the controller, the tracking value is transmitted to the first sub tracking loop 411. The first sub tracking loop 411 continuously updates the signal of the first sub tracking module 311 so that the first sub tracking module 311 can continue tracking when the first sub tracking module 311 acquires the signal again.

3 is a block diagram illustrating in detail a first sub tracking module and a first sub tracking loop included in FIG. 2. 4 is a block diagram illustrating in detail the first sub-tracking module included in FIG. 3. Hereinafter, operations of the first sub tracking module and the first sub tracking loop will be described in detail with reference to FIGS. 1 to 4.

1 to 4, the first sub tracking module 311 includes a carrier removing unit 3111, a code removing unit 3112, and an integration unit 3113. The second and third sub-tracking modules 312 and 313 included in the main tracking module of FIG. 2 are similar, and thus will be omitted.

The carrier removing unit 3111 removes the carrier from the signal of the intermediate frequency output from the RF processing unit 20 based on the control value output from the first sub tracking loop 411. In more detail, the carrier removing unit 3111 includes a carrier generator 31111 and first and second mixers 31112 and 31113. The first and second mixers 31112 and 31113 mix an intermediate frequency signal output from the RF processor 20 and signals output from the carrier generator 31111 to remove a carrier wave from the intermediate frequency signal, thereby removing the I signal and Generate a Q signal. In this case, the carrier generator 31111 generates a carrier wave according to a frequency changed according to a control value output from the first sub tracking loop 411.

The code remover 3112 removes the code from the signal output from the carrier remover 3111 based on the control value output from the first subtrack loop 411. In more detail, the code remover 3112 includes a code generator 31121 and first to sixth mixers 31122, 31123, 31124, 31125, 31126, and 31127. The first to third mixers 31122, 31123, and 31124 may include an I signal output from the carrier remover 3111 and a C / A code generated from the code generator 31121, that is, an early code and a prompt ( prompt) Mix code and rate code to remove the code from the I signal. In addition, the fourth to sixth mixers 31125, 31126, and 31127 may include a Q signal output from the carrier remover 3111 and a C / A code generated from the code generator 31121, that is, an early code, a prompt code, and the like. Mix the rate codes to remove the code from the Q signal. In this case, the code generator 31121 generates a code according to a frequency changed according to a control value output from the first sub tracking loop 411.

The integrator 3113 integrates the signal output from the code remover 3112 by a predetermined integration time unit and outputs a correlation value. More specifically, the integrator 3113 includes first to sixth integrators 31131, 31132, 31133, 31134, 31135, and 31136, where the number of integrators is included in the code remover 3112. It corresponds to the number of mixers. The first to third integrators 31131, 31132, and 31133 output a correlation value that is a correlation result of the I signal and the early code, the prompt code, and the rate code, respectively, and the fourth to sixth integrators 31134, 31135, and. 31136) outputs a correlation value that is a correlation result of the Q signal and the early code, prompt code, and rate code, respectively. As described above, the integration time is set differently for each sub tracking module. Since the integration time of the first sub tracking module 311 is 1 ms, the first to sixth integrators included in the integration unit 3113 are 1 ms. Perform the integration in units.

Referring back to FIG. 2, the position calculation unit 50 uses the GPS receiver 1 using distance measurements and SNRs between the satellite and the receiver output from the first to Nth main tracking loops 41 and 42. Calculate the position of. Specifically, the position calculation unit 50 may determine the distance measurement values L1, L2, L3 from the first to third sub tracking loops 411, 412, and 413 included in the first main tracking loop 41. Receive SNRs SNR1, SNR2, SNR3.

The conventional GPS receiver includes only one channel module without including a plurality of auxiliary channel modules. Thus, if the signal sensitivity is good, the integration time is lowered. If the signal sensitivity is not good, the GPS receiver is increased. To track. As such, increasing the integration time changes the correlation value output from each sub tracking module, thereby reducing the accuracy of the measured distance in each sub tracking loop. In addition, increasing the integration time facilitates tracking of the signal, but results in a relatively large position error.

The first main channel module 31 of the GPS receiver 1 according to an embodiment of the present invention includes a plurality of auxiliary channel modules 311, 312, and 313 having different integration times, and corresponding to the plurality of auxiliary channel modules 31. Since the auxiliary channel loops 411, 412, and 413 of the PSI generate a plurality of distance measurement values using the values output from the respective auxiliary channel modules 311, 312, and 313, the position calculation unit 50 generates a plurality of distance measurement values. All distance measurements are available. That is, the GPS receiver 1 may include a plurality of auxiliary channel modules, thereby obtaining a plurality of distance measurement values for one satellite even when the signal is weak and the sensitivity of the signal is not good. In this case, the position calculator 50 may determine a more accurate position by weighting the plurality of distance measurement values generated in the plurality of auxiliary channel loops 411, 412, and 413.

Accordingly, the position calculator 50 may determine the first to third weights α based on the SNRs SNR1, SNR2, and SNR3 received from the first to third auxiliary channel loops 411, 412, and 413. , β, γ are set, and the optimal position is calculated using the set first to third weights α, β, and γ and the first to third distance measurements L1, L2, and L3. . Specifically, the optimal position value is calculated according to Equation 1 below of the position calculator 50.

[Equation 1]

L = α * L1 + β * L2 + γ * L3

Where L represents the optimal position value. For example, if the signal is low in the first auxiliary channel module 311 having a short integration time due to low sensitivity, the first weight α is set to 0, and the second and third auxiliary channel modules having a long integration time are set to zero. The position is calculated using the second and third distance measurements L2 and L3 based on the correlation value generated at 312 and 313.

5 is a flowchart according to an exemplary embodiment of the present invention for explaining the operation of the position calculator of FIG. 2. Hereinafter, the operation of the position calculator 50 will be described in detail with reference to FIGS. 2 and 5.

In operation 5100, the position calculator 50 determines whether the first SNR SNR1 is greater than the first threshold value TH1. As a result of determination, when the first SNR SNR1 is greater than the first threshold value TH1, step 5200 is performed. Otherwise, step 5300 is performed.

In operation 5200, the position calculator 50 sets the first weight α to 1 since the first SNR SNR1 is greater than the first threshold value TH1, and sets the second and third weights β. , γ) is set to 0. When the first SNR (SNR1) is larger than the first threshold value TH1, the sensitivity of the signal received from the first sub-tracking module 311 having the shortest integration time with 1 ms means that the sensitivity is very good. It is not necessary to use the signal received at the third part tracking modules 312 and 313. Therefore, the position calculator 50 applies the set first to third weights α, β, and γ to Equation 1 and outputs an optimal position to L1.

In operation 5300, the position calculator 50 determines whether the first SNR SNR1 is greater than the second threshold value TH2. Here, the second threshold value TH2 is smaller than the first threshold value TH1. As a result of determination, when the first SNR SNR1 is greater than the second threshold value TH2, step 5400 is performed. Otherwise, step 5500 is performed.

In step 5400, the position calculator 50 sets the third weight γ to 0 since the first SNR SNR1 is between the second threshold value TH2 and the first threshold value TH1. The first and second weights α and β are set using the following equations (2) and (3).

[Equation 2]

α = SNR1 / (SNR1 + SNR2)

[Equation 3]

β = SNR2 / (SNR1 + SNR2)

When the first SNR SNR1 is between the second threshold value TH2 and the first threshold value TH1, the sensitivity of the signal received by the first and second sub-tracking modules 311 and 312 is good. In other words, it is not necessary to use the signal received from the third sub-tracking module 313. Therefore, the position calculator 50 applies the set first to third weights α, β, and γ to Equation 1 and outputs an optimal position as α * L1 + β * L2.

In operation 5500, the position calculator 50 determines whether the second SNR SNR2 is greater than the third threshold value TH3. As a result of determination, when the second SNR SNR2 is greater than the third threshold value TH3, step 5600 is performed. Otherwise, step 5700 is performed.

In operation 5600, the position calculator 50 may determine that the first SNR SNR1 is smaller than the second threshold TH2 and the second SNR SNR2 is greater than the third threshold TH3. (α) is set to 0, and the second and third weights (β, γ) are set using the following equations (4) and (5).

[Equation 4]

β = SNR2 / (SNR1 + SNR2)

[Equation 5]

γ = SNR3 / (SNR2 + SNR3)

If the first SNR (SNR1) is smaller than the second threshold value TH2, it means that the sensitivity of the signal received from the first sub-tracking module 311 is not good, and thus, the first SNR (SNR1) is received from the first sub-tracking module 311. There is no need to use a signal. As a result, the position calculator 50 applies the set second and third weights β and γ to Equation 1, and outputs an optimal position as β * L2 + γ * L3.

In operation 5700, the position calculator 50 may determine that the first SNR SNR1 is smaller than the second threshold TH2 and the second SNR SNR2 is smaller than the third threshold TH3. The second weights α and β are set to zero, and the third weight γ is set to one. When the first SNR SNR1 is smaller than the second threshold TH2 and the second SNR SNR2 is smaller than the third threshold TH3, the first and second sub-tracking modules 311 and 312 may transmit the first SNR SNR1. Since the sensitivity of the received signal is not good, it is not necessary to use the signal received by the first and second sub-tracking modules 311 and 312. As a result, the position calculation unit 50 outputs the optimal position to L3 by applying Equation 1 to the set first to third weights α, β, and γ.

6 is a flowchart illustrating an operation of a position calculator according to another embodiment of the present invention.

In another embodiment of the invention, each primary channel module may comprise two auxiliary channel modules. For example, the first primary channel module 31 may include only the first and second auxiliary channel modules 311 and 312. Hereinafter, the operation of the position calculator 50 in this case will be described in detail.

Referring to FIG. 6, in step 6100, the position calculator 50 determines whether the first SNR SNR1 is greater than the first threshold value TH1. As a result of determination, when the first SNR SNR1 is greater than the first threshold value TH1, step 6200 is performed. Otherwise, step 6300 is performed.

In operation 6200, when the first SNR SNR1 is greater than the first threshold value TH1, the position calculator 50 sets the first weight α to 1 and sets the second weight β to 0. do. When the first SNR (SNR1) is greater than the first threshold value TH1, since the sensitivity of the signal received from the first sub tracking module 311 having the shortest integration time of 1 ms is very good, the second sub tracking is performed. It is not necessary to use the signal received at module 312. Therefore, the position calculator 50 outputs the optimal position to L1 using Equation 1.

In operation 6300, the position calculator 50 determines whether the first SNR SNR1 is greater than the second threshold value TH2. Here, the second threshold value TH2 is smaller than the first threshold value TH1. As a result of determination, when the first SNR SNR1 is greater than the second threshold value TH2, step 6400 is performed. Otherwise, step 6500 is performed.

In operation 6400, the position calculator 50 may determine the first and second weights α and β since the first SNR SNR1 is between the second threshold value TH2 and the first threshold value TH1. Next, Equation 2 and 3 are used. Therefore, the position calculator 50 applies the set first and second weights to Equation 1 and outputs an optimal position as α * L1 + β * L2.

In operation 6500, the position calculator 50 sets the first weight α to 0 and sets the second weight β to 1 since the first SNR SNR1 is smaller than the second threshold value TH2. Set to. If the first SNR (SNR1) is smaller than the second threshold value TH2, it means that the sensitivity of the signal received from the first sub-tracking module 311 is not good, and thus, the first SNR (SNR1) is received from the first sub-tracking module 311. There is no need to use a signal. As a result, the position calculation unit 50 outputs the optimal position to L2 using the set equation (1).

7 is a flowchart illustrating a satellite tracking method according to an embodiment of the present invention.

Referring to FIG. 7, the satellite tracking method according to the present embodiment includes steps processed in time series in the satellite tracking apparatus shown in FIGS. 1 to 4. Therefore, even if omitted below, the above descriptions regarding the satellite tracking devices shown in FIGS. 1 to 4 also apply to the satellite tracking method according to the present embodiment.

In step 710, the plurality of tracking modules mix satellite signals received from one of the plurality of satellites with the duplicated carrier and code. Here, the duplicated code is a duplicated pseudo noise code.

In operation 720, the plurality of tracking modules integrate the mixed results into different integration time units to generate correlation values.

In operation 730, the plurality of tracking loops generate control values for controlling the duplicated carrier and code, distance measurements between the satellite and the satellite tracking device, and SNRs for the satellite signal based on the correlation values.

In operation 740, the location calculator sets weights based on the generated SNRs, and calculates the location of the satellite tracking device by applying the set weights to the distance measurement values.

8A and 8B show errors in position calculated using only the second sub-tracking module in accordance with one embodiment of the present invention. 9A and 9B show errors in position computed using the first and second sub-tracking modules in accordance with one embodiment of the present invention.

8A and 9A show stand-alone positioning errors, where m represents the east of the horizontal axis and the vertical axis represents the north of m. 8B and 9B show 2D rms errors, with the horizontal axis representing time in seconds and the vertical axis representing 2D rms errors in m. First, comparing FIGS. 8A and 9A, it can be seen that the error is much reduced in FIG. 9A using both the first and second sub-tracking modules. Similarly, comparing FIGS. 8B and 9B, it can be seen that the error is reduced in FIG. 9B.

As described above, although the present invention has been described by way of limited embodiments and drawings, the present invention is not limited to the above-described embodiments, which can be variously modified and modified by those skilled in the art to which the present invention pertains. Modifications are possible. Accordingly, the spirit of the invention should be understood only by the claims set forth below, and all equivalent or equivalent modifications will fall within the scope of the invention.

In addition, the system according to the present invention can be embodied as computer readable codes on a computer readable recording medium. The computer-readable recording medium includes all kinds of recording devices in which data that can be read by a computer system is stored. Examples of the recording medium include a ROM, a RAM, a CD-ROM, a magnetic tape, a floppy disk, an optical data storage device, and the like, and also include a carrier wave (for example, transmission through the Internet). The computer readable recording medium can also be distributed over network coupled computer systems so that the computer readable code is stored and executed in a distributed fashion.

1 is a block diagram schematically illustrating a GPS receiver according to an embodiment of the present invention.

FIG. 2 is a block diagram illustrating a part of the GPS receiver of FIG. 1 in detail.

3 is a block diagram illustrating in detail a first sub tracking module and a first sub tracking loop included in FIG. 2.

4 is a block diagram illustrating in detail the first sub-tracking module included in FIG. 3.

5 is a flowchart according to an exemplary embodiment of the present invention for explaining the operation of the position calculator of FIG. 2.

6 is a flowchart illustrating an operation of a position calculator according to another embodiment of the present invention.

7 is a flowchart illustrating a satellite tracking method according to an embodiment of the present invention.

8A and 8B show errors in position calculated using only the second sub-tracking module in accordance with one embodiment of the present invention.

9A and 9B show errors in position computed using the first and second sub-tracking modules in accordance with one embodiment of the present invention.

Claims (20)

In the satellite tracking device, A plurality of tracking modules configured to generate correlation values by performing an integration operation on different integration time units based on satellite signals received from the satellites; A plurality of tracking loops for generating distance measurements between the satellite and the satellite tracking device and signal to noise ratios (SNRs) for the satellite signal based on the correlation values; And And a position calculator configured to set weights based on the SNRs, and apply the weights to the distance measurement values to calculate a position of the satellite tracking device. The method of claim 1, The plurality of tracking modules mix the satellite signal with the duplicated carrier and code, and integrate the mixed result in different integration time units to generate the correlation values, And the plurality of tracking loops generate control values, the distance measurements and the SNRs for controlling the duplicated carrier and code based on the correlation values. The method of claim 2, The plurality of tracking loops may be configured to update a control value for the tracking module that lost the satellite signal by using a correlation value generated by another tracking module when one of the plurality of tracking modules loses the satellite signal. Satellite tracking device. The method of claim 2, The plurality of tracking modules comprises first and second tracking modules, And the first integration time of the first tracking module is set to a period of the code, and the second integration time of the second tracking module is set to a period of data bits. The method of claim 4, wherein The plurality of tracking loops includes a first tracking loop corresponding to the first tracking module and a second tracking loop corresponding to the second tracking module, Wherein the first tracking loop generates a first distance measurement and a first SNR, and the second tracking loop generates a second distance measurement and a second SNR. The method of claim 5, And the position calculator sets weights for the first and second distance measurements by comparing the first SNR with a predetermined threshold. The method of claim 6, The position calculation unit If the first SNR is greater than a first threshold value, the weight for the first distance measurement value is set to 1, Sets the weight for the second distance measurement to 1 when the first SNR is less than a second threshold less than the first threshold, If the first SNR is between the second threshold and the first threshold, the weight for the first distance measurement is a value obtained by dividing the first SNR by the sum of the first and second SNRs. And the weight for the second distance measurement is set to a value obtained by dividing the second SNR by the sum of the first and second SNRs. The method of claim 4, wherein And the plurality of tracking modules further comprises a third tracking module having a third integration time longer than the second integration time. The method of claim 8, The plurality of tracking loops includes a first tracking loop corresponding to the first tracking module, a second tracking loop corresponding to the second tracking module, and a third tracking loop corresponding to the third tracking module, The first tracking loop generates a first distance measurement and a first SNR, the second tracking loop generates a second distance measurement and a second SNR, and the third tracking loop is configured to generate a third distance measurement and Generating a third SNR. The method of claim 9, And the position calculator sets weights for the first to third distance measurements by comparing the first and second SNRs with predetermined thresholds. The method of claim 10, The position calculation unit If the first SNR is greater than a first threshold value, the weight for the first distance measurement value is set to 1, If the first SNR is between a second threshold less than the first threshold and the first threshold, the weight for the first distance measure is the sum of the first SNR and the first and second SNRs. The weight for the second distance measurement is set to the value obtained by dividing the second SNR by the sum of the first and second SNRs. If the first SNR is less than the second threshold and the second SNR is greater than a third threshold, the weight for the second distance measure is the sum of the second and third SNRs. Divided by, the weight for the third distance measurement is set to the value obtained by dividing the third SNR by the sum of the second and third SNRs, And setting the weight for the third distance measurement to 1 when the first SNR is less than the second threshold and the second SNR is less than the third threshold. As a satellite tracking method of a satellite tracking device, Generating correlation values by performing integration operations on different integration time units based on satellite signals received from satellites; Generating distance measurements between the satellite and the satellite tracking device and SNRs for the satellite signal based on the correlation values; And Setting weights based on the SNRs, and applying the set weights to the distance measurement values to calculate a position of the satellite tracking device. The method of claim 12, The generating of the correlation values is performed by a plurality of tracking modules included in the satellite tracking device. When the one of the plurality of tracking modules has lost the satellite signal, updating the control value for the tracking module that lost the satellite signal by using a correlation value generated in another tracking module. Satellite tracking method. The method of claim 13, The calculating of the position may include comparing the SNRs with a predetermined threshold and setting weights for the distance measurements. The method of claim 14, The SNRs include first and second SNRs, The step of calculating the position. Determining whether the first SNR is greater than a first threshold; And And calculating the distance measurement value corresponding to the first SNR as the position of the satellite tracking device when the first SNR is greater than the first threshold value. The method of claim 15, The step of calculating the position, Determining if the first SNR is greater than a second threshold less than the first threshold when the first SNR is less than the first threshold; Calculating a position of the satellite tracking device by setting weights according to the first and second SNRs when the first SNR is greater than the second threshold value; And And calculating the distance measurement value corresponding to the second SNR as the position of the satellite tracking device when the first SNR is smaller than the second threshold. The method of claim 14, The SNRs include first to third SNRs, The step of calculating the position, Determining whether the first SNR is greater than a first threshold; And And calculating the distance measurement value corresponding to the first SNR as the position of the satellite tracking device when the first SNR is greater than the first threshold value. The method of claim 17, The step of calculating the position, Determining if the first SNR is greater than a second threshold less than the first threshold when the first SNR is less than the first threshold; And And calculating the position of the satellite tracking device by setting weights according to the first and second SNRs when the first SNR is greater than the second threshold. The method of claim 18, The step of calculating the position, Determining whether the second SNR is greater than a third threshold when the first SNR is less than the second threshold; Calculating a position of the satellite tracking device by setting weights according to the second and third SNRs when the second SNR is greater than the third threshold value; And And calculating the distance measurement value corresponding to the third SNR as the position of the satellite tracking device when the second SNR is smaller than the third threshold value. A computer readable recording medium having recorded thereon a program for executing the satellite tracking method of claim 12.

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